Keuffel & Esser 4092-3 Log Log Duplex Slide Rule

This ten-inch mahogany two-sided linear slide rule is coated with white celluloid and held together with L-shaped metal end pieces. On one side, the base has K, DF, D, and L scales, with CF, CIF, CI, and C scales on the slide. The right end of the slide is marked in red: < 4092-3 >. The bottom of the base is marked in red: KEUFFEL & ESSER CO. N.Y.; PAT. JUNE 5. '00 DEC. 22. '08 APRIL 1 '24; MADE IN U.S.A. On the other side, the base has LL0, A, LL3, LL2, and LL1 scales, with B, S, T, and C scales on the slide. The left end of the slide and the front of the base are marked with a serial number: 373480.

The indicator is frameless glass with plastic edges held together with metal screws. One edge is marked: K&E.CO.N.Y. (/) PAT.8.17.15. The rule fits in a brown leather case, which is marked on the front of the flap: 4092-3S. The top of the flap is marked: K & E (/) LOG LOG DUPLEX (/) SLIDE RULE. The names of several former owners of the rule are written on the case, including: Bill A.'s; Charles Potter; Theta Xi; Wm. Lund (/) 407 Delaware (/) Ave. (/) Bethlehem Penn.

For information on the patents, see 322761, 318475, and 318479. Keuffel & Esser of New York introduced model 4092-3 in 1922 and in 1925 added a K scale to the rule and an N to the prefix of the model number. The prefix was dropped in 1936, but the indicator was replaced with a new version of K&E's frameless indicator. K&E stopped selling model 4092-3 in 1938, when it was priced with a leather case at $11.75. The serial number on this example is consistent with a manufacture date between 1936 and 1938, but the indicator is of the pre-1936 style. Compare to 1981.0933.01.

References: K&E Slide Rules and Calculating Instruments (New York, 1922), 10–11; K&E Slide Rules and Calculating Instruments (New York, 1925), 10–11; Catalogue of Keuffel & Esser Co., 38th ed. (New York, 1936), 318–319; Ed Chamberlain, "Estimating K&E Slide Rule Dates," 27 December 2000, http://www.sphere.bc.ca/test/ke/320-k+e_date2.jpg.

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